In our patients multicolor FC of pericardial fluid detected the presence of a clonal B cell population suggestive for lymphoma: in the first case an aggressive CD10 + large B cell lymphoma with a peculiar aberrant expression of the CD7 antigen, and in the second case a medium to large-sized B cell lymphoma with partial expression of CD10, and a primary pericardial location. The gene discussed is CD7; the disease is B-cell non-Hodgkin lymphoma.